The Vacuum filtration Nutsche filter is simply an industrial-scale equivalent of the laboratory Buchner funnel.
Nutsche filters consist of cylindrical or rectangular tanks divided into two compartments of roughly the same size, by a horizontal medium supported by a filter plate. Vacuum is applied to the lower compartment, into which the filtrate is collected. It is customary to use the term ‘Nutsche’ only for filters, which have sufficient capacity to hold the filtrate from one complete charge. The cake is removed manually or sometimes by reslurrying.
Depending on the chemical nature of the slurry to be filtered the materials of construction vary from wood, plastics, earthenware, steel, lead-lined steel, to brick-lined cast iron.
Nutsche filters are simple in design, but laborious in cake discharge. They are prone to high amounts of wear due to the digging-out operation. Being completely open, they are quite unsuited for dealing with inflammable or toxic materials. For such applications enclosed agitated Nutsche filters are used.
These filters are particularly advantageous when it is necessary to keep batches separate, and when extensive washing is required, although separation of wash from the mother liquor is difficult. If cake cracking occurs, the cracks can be closed manually for the subsequent washing.